Traditionally, artificial fog had been generated for special effects by the dispersal of various oil chemicals, such as mineral oil. Mineral oil, regardless of the dispersing method used, eventually resulted in a heavy and dangerous deposit of oil on the immediately surrounding surfaces.
Previous devices which attempted to produce a smoke from mineral oil frequently overheated the incoming oil, causing excessive carbon build up within the heating unit and the outlet of the smoke generating device. Of course, it was obvious that this could seriously affect the efficiency of the entire unit.
I have noted that most prior fog generating devices could operate only in the horizontal position. Also, generally, too many special parts had been used in previous devices which had not been compatible with conveniently available effective components, thus making repair or replacement of component parts difficult. This requirement would certainly add to the cost of the device or even to the cost of operation of the device, if the device had to be out of order while waiting for repair.
Frequently, hazardous chemicals had been added to the operating system in an attempt to enhance the hang time of the fog or smoke which had been produced. A portion of these chemicals would remain in the fog or smoke.
Usually, the existent common ground fog machines have required either dry ice or liquid nitrogen as a coolant for the fog material. These are certainly unsafe and dangerous chemicals to be handling. I have designed my system to be much easier and safer to operate.
I have found the following patents which describe various systems for expelling, producing, or dispersing minute particles by means of pressure release, heat application, supercooling, or by practical combinations of certain principles of physics. The patents I found are the following:
______________________________________ U.S. Pat. No. 3,851,146 Bennett Nov. 26, 1974 U.S. Pat. No. 3,986,670 Syveson Oct. 19, 1976 U.S. Pat. No. 4,764,660 Swiatosz Aug. 16, 1988 U.S. Pat. No. 4,818,843 Swiatosz Apr. 4, 1989 U.S. Pat. No. 4,836,452 Fox Jun. 6, 1989 U.S. Pat. No. 5,186,333 Worsfold Oct. 20, 1992 ______________________________________
U.S. Pat. No. 1,851,146 to Bennett describes an apparatus for providing a superheated vapor from an organic liquid which includes a tubular metal member defining a flow passage for both liquid and gaseous phases of the organic compound. A vapor control member is at one end of the tubular member and a source of organic liquid under pressure is provided at the other end of the tubular member. Electric current flows through the tubular member to heat the member and provide heat to vaporize the organic liquid.
U.S. Pat. No. 3,986,670 to Syveson describes a hand held electric fogging device connected to an aerosol container of insecticide. The aerosol container is attached to a housing to which is attached a heat shield having a coiled conduit therein. Electrical heating means are positioned in the area of the coil for heating the solution to be expelled. A lever is provided on the housing to control the heat and to control the output of the container.
U.S. Pat. No. 4,764,660 to Swiatosz describes a portable fog generator which includes a metal conduit for transporting the smoke agent material from a reservoir of the fluid to an outlet orifice. The metal conduit also acts as a resistance heater coil and a thermal sensor. A thermocouple used for calibration is electrically isolated from the coil by a beryllium oxide disk. A pump connected to the reservoir supplies fluid under pressure to the conduit. Smoke producing agents are identified as propylene glycol and polyethylene glycol 200.
U.S. Pat. No. 4,818,843 to Swiatosz describes a smoke generator which has a pump positioned in a housing connected to a source of fluid for generating the smoke. A coiled electrical resistance heating tube has a thin coating of electrical insulating, thermal conducting material, such as boron nitride. The heating tube has one end connected to the pump and the other end forming an outlet for any vapors generated.
U.S. Pat. No. 4,836,452 to Fox describes an artificial fog generator provided with air jet pipes, oil bath, and filtering screens within a housing. An air compressor supplies high pressure air to the device. High pressure air is supplied through the jet pipes above the oil bath and clouds of fine oil bubbles are passed through the filtering screens and then through the outlets.
U.S. Pat. No. 5,156,333 to Worsfold describes a method of producing fog by passing air through a dryer unit to remove moisture, cooling the dried air to a temperature below the freezing point of water by passing the air over a heat exchanger containing liquid nitrogen, and then inducing water vapor into the dried and cooled air to produce the fog.